1. Field of the Invention
The present invention relates to a pressure-regulating valve for supplying a functional liquid to a liquid droplet ejection head, a functional liquid supplying apparatus, an imaging apparatus, a method of manufacturing an electro-optic device, an electro-optic device, and an electronic apparatus.
2. Description of the Related Art
An imaging apparatus in which an ink jet printer as a kind of imaging apparatus is applied to an industrial purpose has a pressure-regulating valve (valve unit for supplying a liquid) which is disposed between a functional liquid tank filled with a functional liquid (ink) and the functional liquid droplet ejection head (ink jet head) in order to give the freedom in a position of installing the functional liquid tank relative to the functional liquid droplet ejection head. The pressure-regulating valve is constituted of: a housing (unit casing); a primary chamber (ink supplying chamber) which is formed by the housing and a first film member thermally welded thereto, and communicates with the functional liquid tank; a secondary chamber (pressure chamber) which is formed by the housing and a second film member (diaphragm) thermally welded thereto, and communicates with the functional liquid droplet ejection head; a communication passage (ink passage) for communicating the primary chamber and the secondary chamber; and a valve disc (movable valve) for opening and closing the communication passage.
A spring-receiving portion is attached to the first film member from the inside thereof, and a valve-disc energizing (or pushing) spring is disposed between the spring-receiving portion and the valve disc to energize the valve disc in a valve-closing direction. Furthermore, a negative-pressure holding spring is disposed between the diaphragm and the housing such that the diaphragm is energized to resist atmosphere from the inside thereof.
When the second chamber has a negative pressure relative to atmospheric pressure as a result of ink ejection from the liquid droplet ejection head, the valve disc is opened in such a way that the diaphragm resists the negative-pressure holding spring and the valve-disc energizing spring. As a result, the functional liquid in the primary chamber flows into the secondary chamber through the communication passage. When the negative pressure of the secondary chamber is canceled after the function liquid is kept flowing, the valve-disc energizing spring pushes back the valve disc to the secondary chamber side, and the negative-pressure holding spring pushes back the diaphragm until it is in the equilibrium state with atmospheric pressure. Accordingly, the valve disc is closed. In this manner, the negative-pressure holding spring and the valve-disc energizing spring expand and contract according to variation in pressure of the primary chamber and the secondary chamber, thereby allowing the functional liquid in the functional liquid tank to be supplied to the liquid droplet ejection head at a constant pressure.
Meanwhile, when a functional liquid having a different specific gravity is used in the pressure-regulating valve, the pressures in the primary chamber and the secondary chamber vary, making it necessary to replace the valve-disc energizing spring and the negative-pressure holding spring so far used with those having repulsion corresponding to the specific gravity of the functional liquid to be used. When a functional liquid having a large specific gravity is used, for example, the pressure generated by the head difference between the liquid droplet ejection head and the valve disc becomes large. As a result, it becomes necessary to increase the force of repulsion of the valve-disc energizing spring to secure improved sealing property of the valve disc. Conversely, when a functional liquid having a small specific gravity is used, it is required to decrease the force of repulsion of the spring. Moreover, the valve-disc energizing spring and the negative-pressure holding spring must be replaced with new ones, because they could be corroded depending on the functional liquid used.
In the conventional pressure-regulating valve, however, the primary chamber having the valve-disc energizing spring accommodated therein is sealed by the first film member and the secondary chamber having the negative-pressure holding spring accommodated therein is sealed by the second film member. Therefore, the springs cannot be replaced independently, thus the entire pressure-regulating valve must be replaced. Alternatively, it is required to change the height of the functional liquid tank and the valve disc. But, such replacing and adjusting operations are liable to make things complicated.